Magistrate Shackleton disagreed and said there was a large element of cruelty by throwing rocks, egging on the dog and hitting the kangaroo in the head.

"For a number of minutes, you were not behaving humanely to that kangaroo," Magistrate Shackleton said.

"In my view, you were having fun tormenting that kangaroo."

Co-offender Jarvis said he had no idea the incident was being filmed and he only joined in to "put it out of its misery".

Police prosecutor Brian McCormack accepted that was "ultimately probably the case" and said Jarvis showed no celebration or jubilation at the end like House did, but that he had still been part of the chase.

Magistrate Shackleton said he was willing to accept Jarvis wanted to put the animal out of its misery but said he had not acted humanely.

"I lobbed rocks to try to get the kangaroo out of the water, I accept that probably wasn't humane," Jarvis said.

House was handed an immediate jail sentence of 11 months while Jarvis was ordered to pay a $10,000 fine.

First jail sentence in WA

RSPCA WA chief executive David van Ooran said it was the first known jail sentence handed down for animal cruelty in WA.

"It's incredibly rare — I can't think of a time in recent years and decades where this has occurred," Mr van Ooran said.

"This is a very strong penalty and a very appropriate penalty ... it was clearly a horrific and sickening act against a defenceless animal, behaviour like this is completely unacceptable.

"It's excellent to see that the magistrate in this case has awarded a prison term."

Mr van Ooran said he hoped the case would set a strong precedent for future cases.

He said the RSPCA was finding the prevalence of smart phone footage was leading to increasingly available evidence to prosecute animal cruelty cases, and they were receiving up to 50 reports per day.